1. Field of the Invention
The present invention relates to a nonaqueous electrolyte battery in which a positive electrode terminal and/or a negative electrode terminal is insulation-sealed to the opening in a metallic exterior member through a ceramic material.
2. Description of the Related Art
In a nonaqueous electrolyte battery, an airtight terminal is provided to connect positive and negative electrodes as electricity-generating elements sealed in the interior of the battery case to the external circuit. As shown in FIG. 4, an example of such a battery is one comprising a positive electrode terminal 1 and a negative electrode terminal 2 insulation-fixed to the battery case, respectively, with a ceramic material 3 provided interposed therebetween. The positive electrode terminal 1 and the negative electrode terminal 2 are each inserted into the respective opening in an external annular metallic member 5 with an annular ceramic material 3 fitted thereon. The positive electrode terminal 1 and negative electrode terminal 2 are each brazed to the ceramic material 3 with filler materials for brazing 4. Further, the ceramic material 3 is brazed to the external annular metallic member 5 with the filler materials for brazing 4. The external annular members 5, 5 are each inserted into the respective opening in a metallic cover 6. These external annular members 5, 5 are each sealed to the opening by welding. The metallic cover 6 is fitted into the upper opening of a metallic container 8 having an electricity-generating element 7 incorporated therein. The metallic cover 6 is sealed to the opening by welding. The positive electrode terminal 1 and the negative electrode terminal 2 are connected to the positive electrode and the negative electrode of the electricity-generating element 7, respectively, at the lower end thereof. Accordingly, the positive electrode and the negative electrode of the electricity-generating element 7 contained in the sealed battery case comprised of a metallic container 8, the metallic cover 6 and the external annular metallic member 5 can be drawn to the exterior of the battery case, respectively, with the positive electrode terminal 1 and the negative electrode terminal 2 insulated by the ceramic material 3.
In a Nixe2x80x94Cd battery or Nixe2x80x94MH battery, as the filler materials for brazing 4 for brazing to the ceramic material 3, there has heretofore been used silver filler material or silver-copper filler material (copper content: 15 to 40%). However, the use of such silver filler material or silver-copper filler material in a nonaqueous electrolytic battery is disadvantageous in that, when the filler materials for brazing 4 with which the positive electrode terminal 1 or the negative electrode terminal 2 is brazed to the ceramic material 3 comes in contact with the nonaqueous electrolyte, the filler material undergoes alloying reaction with an alkaline metal or dissolution reaction to corrode. Consequently, air leakage is caused to thereby shorten the cycle life and calendar life.
It is an object of the present invention to provide a nonaqueous electrolyte battery which has filler materials for brazing coming in contact with the negative electrode terminal a filler material mainly composed of copper and as filler materials for brazing coming in contact with the positive electrode terminal an aluminum alloy based filler material, which filler materials for brazing members are preferably coated with a coating material on the surface thereof which is exposed to the interior of the battery, to prevent the corrosion of the filler materials for brazing more securely.
A first aspect of the present invention concerns a nonaqueous electrolyte battery comprising a negative electrode terminal fixed to an insulating ceramic material with filler materials for brazing mainly composed of copper and insulation-sealed and fixed to the opening in a metallic exterior member with the ceramic material being provided interposed therebetween and/or a positive electrode terminal fixed to an insulating ceramic material with an aluminum alloy-based filler materials for brazing and insulation-sealed to the opening in the metallic exterior member.
The metallic exterior member of the present invention is a member constituting a part of the case of the nonaqueous electrolyte battery, e.g., metallic container, metallic cover and external annular metallic member fitted in the opening in these members.
In accordance with the first aspect of the present invention, a filler material mainly composed of copper, if used as filler materials for brazing coming in contact with the negative electrode terminal, can hardly undergo alloying reaction with lithium or the like, making it possible to prevent corrosion thereof. Further, the use of an aluminum alloy based filler material as filler materials for brazing coming in contact with the positive electrode terminal makes it possible to prevent corrosion due to the dissolution reaction of the filler material even if the filler materials for brazing is at a high potential.
A second aspect of the present invention concerns the foregoing nonaqueous electrolyte battery, wherein the filler materials for brazing mainly composed of copper has a copper content of not less than 50%. In accordance with the second aspect of the present invention, the use of filler materials for brazing having a high copper content makes it possible to prevent air leakage due to the alloying reaction with lithium or the like.
A third aspect of the present invention concerns the foregoing nonaqueous electrolyte battery, wherein the aluminum alloy-based filler material has an aluminum content of not less than 85%. In accordance with the third aspect of the present invention, the use of an aluminum alloy based filler material having a high aluminum content makes it possible to prevent the dissolution reaction of the filler material more securely.
A fourth aspect of the present invention concerns the foregoing nonaqueous electrolyte battery, wherein the negative electrode terminal is made of copper or copper alloy.
A fifth aspect of the present invention concerns the foregoing nonaqueous electrolyte battery, wherein the negative electrode terminal is made of nickel or nickel alloy.
A sixth aspect of the present invention concerns the foregoing nonaqueous electrolyte battery, wherein the positive electrode terminal is made of copper or copper alloy. In accordance with the sixth aspect of the present invention, the positive electrode terminal is made of aluminium or aluminium alloy and thus can be prevented from corroding due to dissolution reaction.
A seventh aspect of the present invention concerns the foregoing nonaqueous electrolyte battery, wherein the filler materials for brazing is coated with a coating material on the surface thereof which is exposed to the interior of the battery. In accordance with the seventh aspect of the present invention, the filler materials for brazing coming in contact with the negative electrode terminal and/or positive electrode terminal is coated with a coating material. Accordingly it is possible to prevent the filler materials for brazing from coming in contact with lithium or the like in the nonaqueous electrolyte and hence prevent corrosion more securely. Further, by coating with the same coating material the filler materials for brazing provided outside the ceramic material which does not come in direct contact with the negative electrode terminal and/or positive electrode terminal, corrosion can be prevented even more securely.
An eighth aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is a polymer. In accordance with the eighth aspect of the present invention, the use of a polymer as a coating material makes it easy to coat the filler materials for brazing. Such a polymer is preferably one which can hardly be dissolved or can hardly swell with the nonaqueous electrolyte. Further, the polymer employable herein may have rubber elasticity.
A ninth aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is a ceramic. In accordance with the ninth aspect of the present invention, the use of a ceramic material having a good corrosion resistance as a coating material makes it possible to prevent the corrosion of the filler materials for brazing more securely. As such a ceramic material, there is preferably used alumina or a ceramic material mainly composed of alumina.
A tenth aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is a ceramic impregnated with a polymer. In accordance with the tenth aspect of the present invention, the impregnation of a ceramic material used as a coating material with a polymer makes it possible to completely prevent the penetration of the nonaqueous electrolyte and thus securely protect the filler materials for brazing. Further, the peeling of the polymer can be prevented.
An eleventh aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is a ceramic coated with a polymer on the surface thereof.
A twelfth aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is a metallic film.
A thirteenth aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is a metallic film formed by plating with Ni or Cu.
A fourteenth aspect of the present invention concerns the nonaqueous electrolyte battery according to the seventh aspect of the present invention, wherein the coating material is prepared by coating with a resin and a metallic film formed by plating with Ni or Cu.